Jraef
Go back to basics for little bit
Stop and think about what going on here.
The speed of an AC motor is determined by the supplied frequency and the number of electrical poles.
As we know we can’ change the number of poles in a motor while is running so the only way to chnge the speed is to change the frequency of the power supplied to the motor.
Base Speed = 120 * Frequency / Number of electrical poles (120 * 50 ) = 6000 / 2 = Motor base speed 3,000 RPM. I assume you read the motor speed with a tach at 2,950 that means the motor is trying to run at 3,000 rpm’s but the motor slip is 50 rpm’s. You must keep in mind that a standard squirrel cage motor will never be able to run at the base speed in this case 3,000 rpm even with no load connected if the motor rpm’s = base speed the torque produced by the motor will be 0 and the rpm’s will slip back
The rpm slip from base speed to actual speed reflects the actual load it called slip
Unless the information posted is wrong then (and I have no reason to believe it’s not correct). All of information and my knowledge of motors tells me it’s clear the motor in this case is a 2 pole motor that can’t be disputed.
The motor amps is a reflection of the work performed by the motor in this case as posted it is 80 amps
Line voltage is 410 VAC so (410 * 80) = 3280 * 1.732) = 56,810 watts or 56.81 KW
In this case the actual power consumed by the motor at this time is 56.81 KW
56,81 / 2 = 28.4 KW that looks real close to the expected 27KW
According to the post the fan should pull 27KW at 40 Amps that number really doesn’t quite add up but close enough.
If you do the math it is 28.257 KW
The fact is that the motor is using over twice the power the fan should be using at it’s rated speed and flow.
Ask yourself this question
What would make a fan motor pull twice the rated amps, the answer is simple, it running at way over the rated speed, nothing else will do that.
Actually I am surprised that the current drawn by the motor in not much higher but I think the drive has reached its max current limit 200% and there in no more current available on the buss for the motor
And it’s limiting the current supplied. If you keep running it at that load the motor will burn up no question about it. Even with a 1.5 service factor but they are almost imposable to find anymore most motors now are 1.0 or 1.15 service factor.
If you recalculate the numbers using a 4 pole motor
((120*50)= 6000 / 4) = a motor base speed of 1, 500 rpm you reduce the speed by 50% this would also reduce the work / load by about the same amount.
It’s telling that power actually used is almost 2 x what it should be. So it would make since a 4 pole motor would reduce the load and bring it down into the expected range.
I keep seeing people on here calling for you to auto tune again why, no auto or manual tune for that matter will make a 50% change in current / power draw of the motor a few amps reduction would be the best you could expect.
We have asked several times for the motor name plate data and the fan curve data but they are never posted. If they were I am sure they would bear out what I am saying.
Motors are rated by Volts to Hertz ratio
410V at 50Hz = 8.2 Volts per Hertz
400V at 50Hz = 8 Volts per Hertz
480V at 60 Hz = 8 Volts per Hertz
An electric motor will draw the amps necessary to do the work asked of it, so you have to limit the work you ask of it. How do you do that on a fan. Simple reduce the speed or restrict the air flow through it.
As I said before on a Fluid load ( Air, Water, Oil are all fluids to a pump) the load (Work required ) goes up by the log of speed. A small increase in speed will make a large increase in power required
As I said before most fans are designed to use a 2 pole motor they are cheaper and easier to build 2 pole verses 4 pole but with the motor running twice a fast but they don’t last as long more ware on the bushings.
The drive should have tripped the OL fault while trying to run so it’s also clear that you have not set the motor full load amps in the drive. Don’t feel too bad about that almost all the jobs I been on lately the FLA on the drives were not set at all.
You should contact the manufacture of the fan or the equipment and get the necessary information and select the correct parts for the job.
An interesting thing to think about: in a vacuum pump as you draw the air out and get closer to a pure vacuum the motor amps actually go down ( Moving less air = less load)
So go right ahead and keep wasting your time playing with the Auto Tune it’s your time to waste.
I offer this to help you and others to understand this, not to put anybody down.